The present invention relates to an impedance-matching network and, more particularly, to an impedance-matching network which can be rapidly, electronically controlled to any one of several possible L-type configurations for impedance-matching a generator to a load over a wide range of frequencies.
Impedance-matching networks for impedance-matching sources to loads are generally well known to those skilled in the art. One well-known type of impedance-matching network includes a plurality of discrete circuits corresponding to a like plurality of frequencies and impedances to which a generator source impedance is to be matched. While this type of impedance-matching network is generally useful, it is limited to load matching transformations over a relatively narrow matched bandwidth. Thus, as the possible operational range of the included frequencies or terminating loads increases, the required number of discrete circuits rises rapidly to a prohibitively large number.
Another well-known type of impedance-matching arrangement includes a rotary or tapped coil which is coupled with a continuously variable capacitor to allow a mechanical adjustment of the reactive elements for permitting the matching of a generator source impedance to a range of terminating impedances. The above type of arrangement has the disadvantage in that the adjustment thereof, being manual and mechanical in nature, is quite slow due the inherent mechanical time constants of the arrangement. A very rapid reconfiguration of the arrangement so as to be used with different load impedances is not achievable since the mechanical components must vary through an initial setting to other settings. This limitation restricts the use of such an arrangement to quasistationary environments where, after an initial adjustment, the terminating impedance and operating frequency remains fixed for a relatively long period of time.